The present invention relates to a securing device for securing two boards to one another in a spatial relationship.
Conventionally, securing devices have been used to secure chassis and printed boards of electrical equipment in electrical isolation. One such conventional securing device is mounted to a chassis by inserting its upper end portion into an aperture in the chassis and securing the printed board on the upper end portion thereof. The conventional securing device comprises a resilient reverse retention member, a linkage member and a pair of resilient legs. The resilient reverse retention member has a larger diameter than that of the chassis aperture for engaging with the outer surface of the chassis after the insertion. The linkage member extends from the center of the concave portion of the resilient reverse retention member and is inserted into the chassis aperture. Resilient legs are provided at both sides of the linkage member. These legs are resiliently deformed during insertion in the aperture and then abruptly allowed to return to their original positions engaging the chassis between the resilient legs and the resilient reverse retention member. When mounted to the chassis, the securing device secures the chassis between the resilient reverse retention member and the resilient legs. The resilient reverse retention member, snapped in place as explained above, is pressed onto the surface of the chassis and is elastically deformed. Therefore, the resilient reverse retention member can adjust to a certain range of thickness in the chassis when mounting the device securely onto the chassis. Furthermore, integrally formed on the upper portion of the linkage member is a structure for being slipped through an aperture in the printed board and supporting the printed board thereon.
The applicant invention is provided with a rectangular linkage member extending from the resilient reverse retention member so that the securing device is enabled to engage a substantially circular aperture in a chassis. In addition, the configurations of the resilient legs provided at both sides of the linkage member are substantially circular to engage a circular aperture. This coherence in shape of the linkage member and the resilient legs realizes strength equal to that of a linkage member having a large diameter. As a further advantage of applicant's invention, since the chassis has a circular aperture therein, the aperture is easy to manufacture and advantageous in the designing of circuit pattern and other boards. In contrast, the prior art securing device has a linkage member having a large circular diameter to increase strength. Since the resilient legs are provided on both sides of the large circular linkage member, an aperture in a chassis has to be elliptic, which is difficult to manufacture, and disadvantageous in designing a circuit pattern and other boards because the aperture is directional.
The prior art securing device has a substantially elliptic aperture and when vibrations are generated during transportation, the two boards (chassis and printed boards) move separately, and this has the tendency to snap the securing device out of the aperture In other cases, the prior art fails because a kinetic energy is generated intently at the base of the linkage member resulting in splits or breakage thereof Because the linkage member is different from the resilient reverse retention member in shape, the internal stress generated by resilient deformation of the resilient reverse retention member intensifies at the junction of the linkage member and the resilient reverse retention member. In addition, the vibration of the boards increases the internal stress beyond a yielding point causing failure.